Miniaturized transducers are fabricated from commercially available four-arm semiconductor gages; transducers are connected as bridge circuit and mounted on internal face of small diaphragm. Jacket made of conductive plastic may be needed to avoid buildup or static charges

Balmer, C. E.

Hwang, C.

Lanham, R. N.

Taylor, C. E.

English

NASA Technical Reports Server

July 1975
	 B75-10145 
S NASA TECH BRIEF Ames Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Mounting Technique for Pressure Transducers

Minimizes Measurement Interferences 
. 
.
The problem: 
The ordinary pressure transducers and mountings 
that are used to measure shock-pressure oscillations 
and other dynamic flow conditions on the wing of an 
aircraft in transonic flight are so large that local flow 
patterns are altered and pressure measurements are 
rendered inaccurate. 
The solution: 
Use miniaturized semiconductor pressure trans- 
ducers housed in a plastic jacket that can be mounted 
smoothly on an aircraft wing. 
How it's done: 
The miniaturized differential pressure transducers 
are fabricated from commercially available four-arm 
semiconductor gages; the transducers are connected 
as a bridge circuit and mounted on the internal face 
of a small diaphragm (0.64 cm). For units which 
have a nominal pressure range of 17,000 N/rn 2 (2.5 
psi) and an o\'errange tolerance of twice the range, 
the transducers typically are about 0.076 cm thick 
and 1.27 cm long. Each transducer includes a refer- 
ence pressure outlet connected to a reference source; 
thermistors and resistors located within the trans- 
ducers provide temperature compensation for the 
dynamic scale factor, but design improvements are 
required if temperature-induced drifts of the null- 
pressure signal must be minimized. 
All transducer harness wires and reference-pres- 
sure tubings are assembled and attached to the wing 
surface; electrical conductors and tubings are led into 
the internal space of the wing structure through rivet 
holes. Strips of 1-mm clear plastic about 30-cm long 
are used to fabricate a jacket for the transducer array;
the plastic strips are machined or undercut to form 
channels which bridge the transducer harnesses and 
tubings, and oversize circular holes are cut in the 
outer surface of the plastic sandwich where pressure 
transducer diaphragm openings are located. A 1 5-to- 
1 taper is cut on the jacket periphery to minimize 
flow interference. The jacket is trimmed, fitted over 
the harnesses and tubings, and bonded by adhesives 
to the wing surface. Then the transducers are con- 
nected to the wirings and tubings and cemented in 
place. Pre-cut metal plugs are fitted in the diaphragm 
holes to act as fillers and to form a smooth airfoil 
surface on the wing. 
A jacket made of conductive plastic may need to 
be used to avoid buildup of static charges, but the 
roughness of a conductive plastic must be taken into 
account when interpreting flow measurements. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: TSP 75-10145 
Patent status: 
NASA has decided not to apply for a patent. 
Source: Ray N. Lanham, Charles E. Taylor,

Carl E. Balmer, and Chintsun Hwang of

Northrop Corporation/Aircraft Division

under contract to

Ames Research Center

(ARC-10933) 
-	 Category 08 
This document was prepared under the sponsorship of the National
	
Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	
will be free from privately owned rights.
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Mounting technique for pressure transducers minimizes measurement interferences

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